Newer central air conditioning units often have two auto settings on their thermostats. Given that you are likely not going to be unsure whether you want it hotter or colder in your home -- and given the fact that the air conditioner or heater will turn on automatically when the thermostat detects a temperature change -- the idea of an auto setting may seem redundant. These two are not, however, and there are times when they are the best settings to use.
Use the auto fan setting when it's humid in the house, or when you want to save energy. The auto fan setting turns the fan on and off along with the air conditioner or heater, so when those aren't on, the fan won't be on, either. That saves energy, as mentioned, and it also stops humid air from being pushed into rooms that aren't being cooled. Your air conditioner will help control humidity in the house when it's on, but when it's off, humidity can seep back into the house along with hot air. Having the fan on when the air conditioner is not on only pushes the humidity into additional rooms.
You also want the fan on auto when the heater is cycling on and off because the fan will simply push cooling air into your room. That's not welcome in winter.
Auto Heat and Cold
The other auto setting controls the thermostat. Most modern thermostats allow you to set the system to heat only, to cool only, or to auto. Auto will turn on the heater if the thermostat detects that the temperature in the house has dropped below what you have as the minimum heat setting. It will turn on the air conditioner instead if the temperature in the house rises above the thermostat setting that you have for the air conditioner.
In hot and cold weather, it doesn't matter whether you use auto or manual settings because you're going to want only one of those on. But in variable weather, when the days may be very hot but the nights very cool, such as you find in desert regions, the auto setting lets you use both systems without having to constantly switch the system yourself.
If you've tried both auto settings and think something isn't working as it should be, have an air conditioning contractor look at your home's system. It could be there's a setting you missed, or there could be a growing problem with the thermostat, compressor, or another part. Once you get those fixed, the auto settings should help you keep your home very comfortable.Share